| From | David Howells <> | Subject | Re: [PATCH 24/64] netfs: Pass more information on how to deal with a hole in the cache | Date | Thu, 09 Dec 2021 16:49:53 +0000 |
| |
JeffleXu <jefflexu@linux.alibaba.com> wrote:
> > @@ -466,7 +466,7 @@ static void netfs_rreq_short_read(struct netfs_read_request *rreq, > > netfs_get_read_subrequest(subreq); > > atomic_inc(&rreq->nr_rd_ops); > > if (subreq->source == NETFS_READ_FROM_CACHE) > > - netfs_read_from_cache(rreq, subreq, true); > > + netfs_read_from_cache(rreq, subreq, NETFS_READ_HOLE_CLEAR); > > Hi I'm not sure why NETFS_READ_HOLE_CLEAR style should be used in 'short > read' case.
The cache backing filesystem (eg. ext4) might have excised a chunk of zeros from the cache in order to optimise its extent list. This instructs the cache to zero over the cracks. Actually, I need to think a bit further on this. This was written assuming that the cache tracks its content independently - but those patches are not in with this set.
> I'm not sure why 'subreq->start' is not incremented with > 'subreq->transferred' when calling cres->ops->read() in 'short read' case.
subreq->start shouldn't get changed. subreq->transferred is sufficient.
David
|